Conventionally, among game machines, pachinko game machines are endlessly subjected to deceit actions in which prize balls are unfairly obtained, and various prevention measures have been taken. Particularly, the control board housing box for housing the control board is provided with various arrangements for preventing unauthorized modifications to a control board which controls the game machine, for example, for preventing replacement to an unauthorized ROM. For example, the control board housing box is provided with a seal. In a pachinko game machine described in Japanese Laid-Open Patent Publication No. 10-216324, the control board hosing box is hard to open because it is provided with a seal screw which rotates only to a tightening direction along which the control board housing box is closed in order to make the main control board untouchable. In a pachinko game machine described in Japanese Laid-Open Patent Publication No. 9-34365, opening and closing operations to the housing box are detected using a movable contact point, and the detection signal from the movable contact point is stored and is annunciated by a light emitting diode. In a game device described in Japanese Laid-Open Patent Publication No. 2000-288218, an IC tag is attached onto the surface of the control board housing box. In response to a request for transmission from an ID read unit, the IC tag is allowed to transmit identification information stored therein to the ID read unit. It is determined by confirming the identification information whether or not the control board housing box, involving the control board, has been entirely replaced unfairly.
However, in the arrangement using the seal, if the control board housing box is opened and a ROM is replaced with an unauthorized one, and then a sophisticated imitation seal is attached, it is hard to determine whether or not the control board housing box has been opened and then closed. In the arrangement using a seal screw, there are some cases where the seal screw is forcibly turned to its opening direction by means of a special tool to open the control board housing box and a ROM is replaced with an unauthorized one. Further, in the arrangement in which the opening and closing operations to the control board housing box are detected using the movable contact point, since the control board housing box is usually made of a transparent resin, the presence of the movable contact point for use in detecting the opening and closing operations to the housing box can be visually seen. Therefore, there are some cases where a piano wire or the like is inserted through the clearance of the board housing box so as to prevent the movable contact point from moving. In this case, there arises a problem that the opening and closing operations to the control board housing box cannot be detected. Further, these above-described prior arts have a problem that whether or not the control board housing box has been opened and closed can be determined only when the control box is visually checked. In many cases, deceit actions are made at night and it is cumbersome to inspect and check each of several hundreds of game machines in an amusement center every morning. In the arrangement in which the unauthorized replacement of the control board housing box is monitored by identifying the IC tag, since the ID read unit is placed outside of the control board housing box, it is possible to open the control board hosing box without changing the relative position between the IC tag and the ID read unit so as to replace the ROM on the housed control board with an unauthorized one. Eventually, this arrangement is not sufficient to detect deceit actions at an early stage.